Not to knock that air grinder, I have not used one I so I can't say anything good or bad about it but every cheap air die grinder I have seen runs rough (out of balance) and will cause the stone or burr to "bounce" which will cause poor cutting action and extremely short stone/burr life, again not saying that is the case with that one however. I like the electric grinders better because they seem to have more power and the air powered ones are usually quite air hungry for the work they do but often you can use an air grinder where the electric one simply will not fit plus it is easy to control the speed of the air grinder. For less than $20 I guess I will just find out for myself next time I get over there.